6.20.17 strncmp Function

Compare two strings, up to a specified number of characters.

Include

<string.h>

Prototype

int strncmp(const char *s1, const char *s2, size_t n);

Arguments

s1

first string

s2

second string

n

maximum number of characters to compare

Return Value

Returns a positive number if s1 is greater than s2, zero if s1 is equal to s2 or a negative number if s1 is less than s2.

Remarks

strncmp returns a value based on the first character that differs between s1 and s2. Characters that follow a null character are not compared.

Example

See the notes at the beginning of this chapter or section for information on using printf() or scanf() (and other functions reading and writing the stdin or stdout streams) in the example code.

#include <string.h>
#include <stdio.h>

int main(void)
{
  char buf1[50] = "Where is the time?";
  char buf2[50] = "Where did they go?";
  char buf3[50] = "Why?";
  int res;

  printf("buf1 : %s\n", buf1);
  printf("buf2 : %s\n", buf2);
  printf("buf3 : %s\n\n", buf3);

  res = strncmp(buf1, buf2, 6);
  if (res < 0)
    printf("buf1 comes before buf2\n");
  else if (res == 0)
    printf("6 characters of buf1 and buf2 "
           "are equal\n");
  else
   printf("buf2 comes before buf1\n");
  printf("\n");

  res = strncmp(buf1, buf2, 20);
  if (res < 0)
    printf("buf1 comes before buf2\n");
  else if (res == 0)
    printf("20 characters of buf1 and buf2 "
           "are equal\n");
  else
    printf("buf2 comes before buf1\n");
  printf("\n");

  res = strncmp(buf1, buf3, 20);
  if (res < 0)
    printf("buf1 comes before buf3\n");
  else if (res == 0)
    printf("20 characters of buf1 and buf3 "
           "are equal\n");
else
    printf("buf3 comes before buf1\n");
}

Example Output

buf1 : Where is the time?
buf2 : Where did they go?
buf3 : Why?

6 characters of buf1 and buf2 are equal

buf2 comes before buf1

buf1 comes before buf3